This invention relates to suspension systems and more particlarly to a fluid suspension system for tractor-scraper combinations or like vehicles.
A hydraulic suspension system for tractor-scraper combinations has been suggested which comprises a jack connected between the vehicle body and a suspension frame or arm pivotally connected at one end to the vehicle body and carrying each vehicle wheel at another end, as disclosed for example in Japanese Patent Publication No. 48-16802. Associated with an accumulator to provide a cushioning system, the jack is selectively vented or supplied with hydraulic fluid via a height control valve. This height control valve is actuated by a linkage system connecting its spool to the suspension frame.
According to this prior art construction, the height control valve is easy to be actuated accidentally as the vehicle encounters irregularities in the road, with the consequent swinging motion of the suspension frame relative to the vehicle body. Although the mentioned Japanese patent employs a spring to circumvent this defect, it is insufficient to prevent the valve from unnecessary actuation, thus resulting in wasteful use of the pump pressure.